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应用真空电弧熔炼方法制备La-Mg-Ni/Co5:19和2:7型储氢合金.应用X射线衍射系统研究这两类合金的相结构,并测定各相的原子占位.研究表明:5:19型的(La1-xMgx)5Co19合金是由Pr5Co19,LaCo5和LaSb3V3种类型结构组成;在2:7型的(La1-xMgx)2Ni7合金中,除了(La0.85Mg0.15)2Ni7合金只含LaNi5类型相结构外,其他合金均含有LaNi5类型相结构及LaNi3或La2Ni7类型相之一.应用尝试法确定合金中各相的晶胞参数和体积的变化规律,并利用Rietveld全谱拟合分析方法测定了(La0.95Mg0.05)2Ni7合金的相结构及相含量.研究表明:两种储氢合金相结构中主相与晶界相的点阵常数之间存在良好的共格性.Mg原子同时部分取代La和Ni原子,随着Mg含量的增加,晶胞内空隙变大.由于吸收的H原子将占据这些空位,所以空位空间的增加有助于容纳更多的H.这暗示Mg原子的占位导致的晶体畸变与储氢合金储氢能力相关,同时由于Mg原子与H原子之间强的亲和力,以及主相与晶界相之间的共格关系,可以使得H原子更容易进人合金中,并形成稳定的相结构.
La-Mg-Ni / Co5: 19 and 2: 7 hydrogen storage alloys were prepared by vacuum arc melting method.The phase structures of these two alloys were investigated by X-ray diffraction and the atomic occupancy of each phase was determined.The results show that: The 5:19-type (La1-xMgx) 5Co19 alloy is composed of three types of Pr5Co19, LaCo5 and LaSb3V structures. In the La7Mgx2Ni7 alloy of the 2: 7 type, LaNi5-type phase structure, LaNi5-type phase structure and LaNi3 or La2Ni7 phase.According to Rietveld full-spectrum fitting analysis, the change law of unit cell parameters and volume of each phase in the alloy was determined by the try method, The phase structure and phase content of (La0.95Mg0.05) 2Ni7 alloy have been measured.The results show that there is a good coherence between the lattice constants of the main phase and the grain boundary phase in the two hydrogen storage alloys, Atoms are simultaneously partially substituted for La and Ni atoms, and as the Mg content increases, the intragranular voids become larger.As the absorbed H atoms will occupy these vacancies, an increase in vacancy space helps to accommodate more H. This suggests that Mg The crystal distortion caused by the occupancy of atoms is related to the hydrogen storage capacity of hydrogen storage alloys. At the same time, due to the interaction between Mg atoms and H The strong affinity between the sub, and the coherent phase relationship between the main phase and the grain boundary, so that H atoms may be easier into the alloy, and form a stable phase structure.